1. Field of the Invention
The present invention relates to an audio plug used for utilizing an audio equipment equipped on a vehicle or the like by plugging into a jack.
2. Description of the Related Art
Heretofore, in a vehicle such as an aircraft, a headset is used to listen to music or audio of a movie, wherein an earphone or a headphone is worn on the ears or head of a user, and a plug disposed on an end of a cable extending from a speaker portion of the earphone or headphone is plugged into a jack disposed on or around a passenger seat. FIG. 4 shows one example of a prior-art two plug-type audio plug included in a headset. FIG. 4(a) is a plan view of the two plug-type audio plug, and FIG. 4(b) is a front view thereof. An audio plug 80 illustrated in FIG. 4 has a flexible cable 83 connected to an end of a plug body 82 having high rigidity via a connecting portion 85 that takes the form of a protection bushing. On the plug body 82, two channel plugs for stereo, that are, a mutually parallel left channel plug 86 and a right channel plug 87, are perpendicularly protruded from the plug body 82.
FIG. 5 shows one example of a prior-art single plug-type audio plug. FIG. 5(a) is a plan view of the single plug-type audio plug, and FIG. 5(b) is a front view thereof. Same reference numbers are provided to the components of audio plug 90 shown in FIG. 5 that are equivalent to the components of FIG. 4, and explanations thereof are omitted. In a single channel plug 91, the base-side contact is a left channel contact portion 92, and the distal end-side contact in the axial direction of the-plug is a right channel contact portion 93, wherein the two channel contact portions 92 and 93 are separated by insulating collars 94 and 95.
The headset for a vehicle mentioned above is suitable for listening to music and audio programs without causing inconvenience to the other passengers, but there sometimes occur problems in which one of the channels cannot be heard or a noise is mixed in. The main cause of these problems is considered to be the poor contact or disconnection occurring at the contact portion between the plug body having high rigidity and the flexible cable. Such malfunction is mostly caused by excessive force being applied from the cable to the plug still plugged into to the jack, such as when a passenger wearing the headset on his/her head stands up from the seat with the plug on the cable still plugged into the jack, or when a baggage or the like loads a large force on the cable. That is, since the plug connected to the jack is structured so that the plug will not be removed from the jack unless it is pulled out in an appropriate fashion, an attempt to force the plug to be removed from the jack causes excessive stress to be applied to the connection from the cable to the plug, which is assumed to be the cause of poor contact and disconnection.
A plug, a headphone and a support method for the headphone are proposed (Japanese Patent Application Laid-Open Publication No. 2001-128277 (columns 0016 through 0018 and FIG. 3), hereinafter referred to as patent document 1), in which a headphone is constituted of two receiver portions, a belt connecting the receiver portions, a cable connected to both receiver portions, and a plug disposed on the end of the cable that can be inserted to a jack, wherein a drum with a prescribed width is provided at a middle portion of the plug in the longitudinal direction, and the belt can be hung from the drum with the plug plugged into the jack so as to support the headphone using the plug.
When handling the headset, there is a fairly small possibility of poor contact or disconnection of the plug occurring as long as the passenger pays sufficient attention to the plug, but if the passenger is enjoying the music, he/she may not be conscious that the plug of the headset is plugged into the jack, and it is inevitable that the sudden move of the passenger wearing the headset, such as significant change of head position or standing from the seat, causes stress to be applied to the connection between the cable and plug body. There is a need to apply pulling force from an appropriate direction to unplug the channel plug from the jack, but in most cases where excessive force is applied on the plug from the cable, the force is not applied in the appropriate unplugging direction.
In the field of load appliances such as an electric hot water pot, a magnet plug is used as the plug for supplying electric power so that the plug is easily unplugged from the load appliance when the electric cord is pulled. A magnet plug is proposed (Japanese Patent Application Laid-Open Publication No. 05-054932, hereinafter referred to as patent document 2) in which the connection pin is prevented from being stuck when the plug body rotates while receiving pulling force from the electric cord, by defining the inner diameter of the pin insertion hole formed to the plug body. Another proposal (Japanese Patent Application Laid-Open Publication No. 05-205811, hereinafter referred to as patent document 3) proposes selecting the type of protection bushings for connecting the electric cord to the plug body in order to correspond to cases where the pullout directions of the electric cord differ. Moreover, a proposal is made (Japanese Patent Application Laid-Open Publication No. 2002-056929, hereinafter referred to as patent document 4) in which a projection having a slanted surface is provided to an outer surface of the plug body case and having the slanted surface contact the opening end of a plug receiver at the equipment when the plug is slanted, so as to enable the plug to be easily removed from the plug receiver. Even further, there exists a proposal (Japanese Utility Model Registration No. 2570950, hereinafter referred to as patent document 5) in which a magnet plug is connected to the equipment at an inner position than the bottom outer circumference surface of the equipment body, thereby preventing the magnet plug from being removed or the connection failure from occurring by the walls surrounding the equipment.
Thus, the problem to be solved is to enable the channel plug to remain plugged to the jack while enabling only the plug body to be removed by small force from a component equipped with the channel plug, when an excessive force is caused to be applied to the plug from the cable.